Basal cell skin carcinoma: Epidemiology of locally advanced and metastatic forms based on the data of the N.N. Blokhin National Medical Research Center of Oncology: A retrospective study

Background. Basal cell skin carcinoma (BCSC) is the most common skin cancer. Most cases are diagnosed early and successfully treated using local methods. However, a small proportion of patients develop locally advanced or metastatic BCRCs, which is a challenging clinical issue. The number of locally advanced and/or metastatic forms of BCSCs is based on the experience of individual centers or the analysis of individual databases because the skin cancer cases generally are coded and accounted under the C44 category without counting separately the nosological forms and data on the disease prevalence. Aim. To estimate the number of patients with locally advanced and metastatic BCRCs among all patients treated in the N.N. Blokhin National Medical Research Center of Oncology from 2019 to July 2024 with the diagnosis code C44 according to the International Classification of Diseases, 10th Edition. Results. Between 2019 and July 2024, 3,801 individual cases of non-melanoma skin cancer (C44) were reported. Most of the 3,801 patients had BCSCs (n=2,796, 73.6%), followed by squamous cell carcinoma (n=857, 22.5%), Merkel cell carcinoma (n=100, 2.6%), and other skin tumors and neoplasms originating from the skin appendages (n=48, 1.3%). Among all cases of BCSCs, 94 (3.4%) cases of locally advanced and metastatic forms of the disease were reported. These patients were divided into two groups: with locally advanced BCSC (78 patients, 2.8%) and metastatic BCSC (16 patients, 0.6%). Conclusion. Most patients with early stages of BCSCs can be completely cured with radical surgery and/or radiation therapy, and a small number of patients develop disease progression that is not amenable to surgery or radiation therapy. We obtained the following results: 2.8% of locally advanced BCSCs and 0.6% of metastatic BCSCs, which is consistent with the literature data, where locally advanced BCSCs are reported in 1-2% of patients, and BCSC metastasis is reported in 0.0028-0.55%.